The present invention relates to a vehicle speed control system for controlling a vehicle speed, and more particularly to a vehicle speed control system which controls an automotive vehicle so as to automatically cruise the automotive vehicle at a target vehicle speed.
A typical vehicle speed control system is arranged to suspend a vehicle cruise control when the vehicle is accelerated over a target vehicle speed by the depression of an accelerator pedal, and to restart the vehicle cruise control when the throttle opening is returned to a set throttle opening for the cruise control.
Accordingly, the vehicle cruise control is restarted from a traveling condition at a vehicle speed higher than the target vehicle speed, and therefore the vehicle speed is decreased to the target vehicle speed by closing a throttle.
However, such a typical vehicle speed control system has executed the deceleration control at this restart of the cruise control without employing a transmission and a brake system. Therefore, when the vehicle requires a further deceleration in addition to the deceleration due to the throttle control, such as during a down slope traveling, a conversion to the target vehicle speed is not suitable. Further, if the vehicle is equipped with an automatic transmission except for a continuously variable transmission, the utilization of the deceleration due to the non CVT automatic transmission will cause shift shocks which will apply unsuitable feeling to vehicle occupants. Further, if the deceleration due to the brake system is employed during the down slope traveling, the brake system will cause the brake fade and will degrade the braking performance of the brake system.
It is therefore an object of the present invention to provide an improved vehicle speed control system which is capable of quickly decelerating the vehicle from an over target speed to a target vehicle speed without generating shift shocks and the brake fade.
A vehicle speed control system according to the present invention is for a vehicle equipped with an engine and a continuously variable transmission (CVT). The vehicle control system comprises a controller which is arranged to execute a vehicle speed control for bringing a vehicle speed closer to a target vehicle speed, to suspend the vehicle speed control when a throttle opening is increased to an opening which is greater than a target throttle opening for the vehicle speed control, to restart the suspended vehicle speed control when the throttle opening becomes smaller than the target throttle opening, and to decrease the throttle opening and to execute a shift down of the CVT when the vehicle speed at the moment of restarting the vehicle speed control is greater than or equal to the target vehicle speed.